Precursor compositions for an insulation, insulated rocket motors, and related methods

ABSTRACT

A precursor composition comprising, before curing, ethylene propylene diene monomer (EPDM), an aramid, and a carbon material comprising carbon nanotubes, graphite, or a combination thereof. A rocket motor including a reaction product of the precursor composition and a method of insulating a rocket motor are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is related to U.S. Ser. No. 15/461,339, filedMar. 16, 2017, entitled “PRECURSOR COMPOSITIONS FOR AN INSULATION,INSULATED ROCKET MOTORS, AND RELATED METHODS,” pending; and to U.S. Ser.No. 15/726,731, filed Oct. 6, 2017, entitled “PRECURSOR COMPOSITIONS FORAN INSULATION, INSULATED ROCKET MOTORS, AND RELATED METHODS,” pending.

TECHNICAL FIELD

Embodiments of the disclosure relate to a precursor composition of aninsulation for use in an article and to methods of insulating thearticle. More particularly, embodiments of the disclosure relate to aprecursor composition including an aramid for an insulation for use invarious locations on rocket motors or other articles and methods ofinsulating a rocket motor or other article.

BACKGROUND

Rocket motors include a case that houses an energetic fuel, which mayalso be characterized as a propellant. An insulation and an optionalliner protect the case interior from thermal and erosive effects ofparticle streams generated by combustion of the energetic fuel orpropellant. The rocket motor includes a nozzle operatively associatedwith the case to receive combustion products generated by combustion ofthe propellant and to expel the combustion products, generating thrustto propel the rocket motor and associated aerospace vehicle. Theinsulation is bonded to an interior surface of the case and isfabricated from a composition that, upon curing, is capable of enduringthe extreme temperature, pressure, and turbulence conditions producedwithin the case. High temperature gases and erosive particles areproduced with the case during combustion of the energetic fuel orpropellant. During use and operation, the temperatures inside the casemay reach about 2,760° C. (about 5,000° F.), pressures exceed about1,500 pounds per square inch (“psi”) (about 10.3 MPascal), andvelocities of gases reach or exceed Mach 0.2. These conditions, alongwith a restrictive throat region provided along a passageway between thecase and the nozzle, combine to create a high degree of turbulencewithin the case. In addition, the gases produced during combustion ofthe fuel or propellant contain high-energy particles that, under aturbulent environment, erode the insulation. Additionally, if the fuelor propellant penetrates through the insulation, the case may melt, beeroded, or otherwise be compromised, causing the rocket motor to fail.

Depending on the configuration of the rocket motor, various combinationsof mechanical, thermal, and ablative properties are desired in differentsections of the rocket motor. For some sections, high elongationproperties are desirable while for other sections, good ablation and/orgood mechanical properties are desirable. Some sections need goodelectrostatic discharge (ESD) properties, while other sections need goodinsulative properties. To provide the desired properties, conventionalrocket motors employ different insulations in different sections of therocket motor. However, using different insulations adds to the cost andcomplexity of manufacturing the rocket motor because multipleformulations must be produced and applied to the rocket motor. Theinsulations also include fibers or lack fibers depending on the desiredmechanical, thermal, and ablative properties needed in the differentsections. Asbestos fibers, glass fibers, carbon fibers, basalt fibers,aramid fibers, polybenzamide fibers, polybenzimidazole fibers, orpolybenzoxazole fibers have been used in fiber-filled insulations.

BRIEF SUMMARY

Disclosed is an embodiment of a precursor composition comprising, beforecure, ethylene propylene diene monomer (EPDM), an aramid, and a carbonmaterial comprising carbon nanotubes, graphite, or a combinationthereof.

Also disclosed is an embodiment of a precursor composition comprising,before cure, ethylene propylene diene monomer (EPDM), aramid fibers, acarbon material, an antioxidant, a chlorinated organic compound, afiller selected from the group consisting of zinc oxide, silica,magnesium hydroxide, and combinations thereof, stearic acid, a fivecarbon petroleum hydrocarbon, trimethylolpropane trimethacrylate or apoly(butadiene) resin, and1,1-di-(t-butylperoxy)-3,3,5-trimethylcyclohexane) polymer or dicumylperoxide.

A rocket motor is also disclosed and comprises a case, an insulation onat least a portion of the case, and a propellant in the case. Theinsulation comprises a reaction product of ethylene propylene dienemonomer (EPDM), an aramid, and a carbon material comprising carbonnanotubes, graphite, or a combination thereof.

A method of insulating a rocket motor is also disclosed. The methodcomprises applying a precursor composition of an insulation to at leasta component of a rocket motor and curing the precursor composition toform the insulation. The precursor composition comprises ethylenepropylene diene monomer (EPDM), an aramid, and a carbon materialcomprising carbon nanotubes, graphite, or a combination thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a rocket motor including aninsulation formed from a precursor composition according to anembodiment of the disclosure;

FIG. 2 is an enlarged view of the portion of the rocket motor encircledin FIG. 1;

FIGS. 3-5 are photographs showing the flow properties of insulationsaccording to embodiments of the disclosure in a spider mold;

FIGS. 6-8 are photographs showing the extrusion properties of precursorcompositions of the insulation according to embodiments of thedisclosure;

FIGS. 9-11 are plots of the material ablation rate (mm/s) versus chamberlocation (inches) of the insulation formed from the precursorcompositions according to embodiments of the disclosure from the low,mid, and high sections of the SPC motor test;

FIGS. 12-14 are bar graphs showing weight loss (percent weight loss)from a seventy pound char (SPC) motor test of low, mid, and highsections of the char motor having insulation formed from the precursorcompositions according to embodiments of the disclosure; and

FIGS. 15-17 are bar graphs showing the average material ablation rate(mm/s) of the insulation formed from the precursor compositionsaccording to embodiments of the disclosure from the low, mid, and highsections of the SPC motor test.

DETAILED DESCRIPTION

An insulation formed from a precursor composition including a polymer ofethylene propylene diene monomer (EPDM), an aramid, and a carbonmaterial is disclosed.

When used to insulate a rocket motor or other article to be insulated,the insulation may be characterized as “universal” in that the sameinsulation may be used on different regions of the particular rocketmotor or article that require insulation. The universal insulation isformulated to protect different regions of the rocket motor or articlethat need protection from one or more of heat, erosion, and otherextreme conditions experienced during use and operation of the rocketmotor or other article. The universal insulation may be used as internalinsulation of the rocket motor or other article, external insulation ofthe rocket motor or other article, or as a shear ply to couple a case ofthe rocket motor to a rocket skirt. The universal insulation providesimproved or comparable mechanical, physical, rheological, thermal, andablative properties compared to conventional aramid-filled EPDM-basedinsulations, while including fewer ingredients than the conventionalaramid-filled EPDM-based insulations. By using the universal insulationhaving substantially similar or identical ingredients in multiplelocations of the rocket motor, the cost and complexity of manufacturingthe rocket motor or other article is reduced. Different regions of therocket motor or article may also include the universal insulation havingsimilar or identical ingredients except lacking the aramid.

The precursor composition of the insulation includes the EPDM, thearamid, the carbon material, an antioxidant, one or more fillers, aflame retardant, a processing aid, a plasticizer, a co-agent, and acurative. The ingredients of the precursor composition of the insulationare commercially available and, therefore, are less likely to becomeobsolete. As used herein, the term “precursor composition” means andincludes ingredients of the composition before the ingredients arereacted (e.g., cured). Curing the precursor composition forms theinsulation, which may then be applied to the rocket motor or otherarticle.

As used herein, the terms “comprising,” “including,” “containing,”“characterized by,” and grammatical equivalents thereof are inclusive oropen-ended terms that do not exclude additional, unrecited elements ormethod acts, but also include the more restrictive terms “consisting of”and “consisting essentially of” and grammatical equivalents thereof. Asused herein, the term “may” with respect to a material, structure,feature or method act indicates that such is contemplated for use inimplementation of an embodiment of the disclosure and such term is usedin preference to the more restrictive term “is” so as to avoid anyimplication that other, compatible materials, structures, features andmethods usable in combination therewith should or must be excluded.

As used herein, the term “substantially” in reference to a givenparameter, property, or condition means and includes to a degree thatone of ordinary skill in the art would understand that the givenparameter, property, or condition is met with a degree of variance, suchas within acceptable manufacturing tolerances. By way of example,depending on the particular parameter, property, or condition that issubstantially met, the parameter, property, or condition may be at least90.0% met, at least 95.0% met, at least 99.0% met, at least 99.9% met,or even 100.0% met.

The illustrations presented herein are not meant to be actual views ofany particular device, but are merely idealized representations that areemployed to describe the present disclosure. The figures are notnecessarily drawn to scale. Additionally, elements common betweenfigures may retain the same numerical designation.

The EPDM is a terpolymer of ethylene, propylene, and a non-conjugateddiene. The non-conjugated diene may include, but is not limited to,ethylidene norbornene (ENB). The EPDM may be linear or branched, e.g.,including controlled long chain branching (LCB). Using a linear EPDM orbranched EPDM may affect the extent of crosslinking of the precursorcomposition following cure in addition to properties of the uncuredprecursor composition and cured precursor composition. The EPDM may havea diene content of from about 1% by weight (wt %) to about 10 wt %, suchas about 5.0 wt %. In some embodiments, the EPDM has a diene content ofabout 5.0 wt %. In another embodiment, the EPDM has a diene content ofabout 6.0 wt %. The EPDM may have an ethylene content of greater thanabout 40 wt %, such as between about 40 wt % and about 85 wt %, betweenabout 40 wt % and about 75 wt %, or between about 45 wt % and about 55wt %. In some embodiments, the EPDM has an ethylene content of about 50wt % or about 53 wt %. The EPDM may be commercially available from DowChemical Company (Midland, Mich.) under the NORDEL® tradename or fromLANXESS Deutschland GmbH (Marl, Germany) under the KELTAN® tradename. Byway of example only, the EPDM may be NORDEL® IP 4520 or KELTAN® 2650.However, other EPDM materials having the above properties may be used,which reduces obsolescence issues. The EPDM may be present in theprecursor composition of the insulation at from about 70 parts to about150 parts, such as from about 50 parts to about 120 parts or from about60 parts to about 110 parts. In some embodiments, the EPDM is NORDEL® IP4520, has a diene content of about 5.0 wt %, an ethylene content ofabout 50.0 wt %, and is present in the precursor composition of theinsulation at about 65.8 parts. In other embodiments, the EPDM isKELTAN® 2650, has a diene content of about 6.0 wt %, an ethylene contentof about 53 wt %, and is present in the precursor composition of theinsulation at about 80.5 parts or about 100 parts.

The aramid (also known as an aromatic polyamide, a polyaramid, orpara-aramid) in the precursor composition may be poly-p-phenyleneterephthalamide, poly-m-phenylene isophthalamide,copoly-p-phenylene-3,4′-oxydiphenylene-terephthalamide, or mixedaliphatic-aromatic polyamides, such as poly-m-xylylene adipamide,poly-m-xylylene pimelamide, poly-m-xylylene azelamide, poly-p-xylyleneazelamide, poly-p-xylylene decanamide, or combinations thereof. In someembodiments, the aramid comprises poly-p-phenylene terephthalamide. Thearamid may be present in the precursor composition of the insulation atfrom about 5.0 parts to about 25.0 parts, such as from about 10.0 partsto about 15.0 parts, from about 10.0 parts to about 20.0 parts, fromabout 15.0 parts to about 20.0 parts, from about 15.0 parts to about25.0 parts, or from about 20.0 parts to about 25.0 parts. In someembodiments, the aramid is present at about 11.0 parts. In otherembodiments, the aramid is present at about 20.0 parts. In otherembodiments, the aramid is present at about 21.0 parts.

The aramid may be used in fiber form. By way of example only, the aramidmay be poly-p-phenylene terephthalamide fibers, such as thosecommercially available under the TWARON® tradename from Teijin AramidB.V. (Arnhem, Netherlands). The poly-p-phenylene terephthalamide fibersexhibit high strength-to-weight properties, high modulus, highdimensional stability, low flammability, a highly crystalline structure,and no melting point. In some embodiments, the aramid is a pulp form ofTWARON® 1099 para-aramid. The TWARON® 1099 para-aramid has a specificsurface area in a range of from about 9 m²/g to about 13 m²/g with afiber length of from about 0.9 mm to about 1.35 mm and a moisturecontent of from about 4% by weight to about 8% by weight.

While the aramid is described herein as being poly-p-phenyleneterephthalamide fibers, other forms of poly-p-phenylene terephthalamidemay be used including, but not limited to, filament yarn, staple fiber,pulp, paper, short-cut fiber, fabric, laminate, powder, or tape. In someembodiments, the pulp form of the poly-p-phenylene terephthalamidefibers is used. The pulp form is produced from a filament yarn that iscut, suspended in water, and fibrillated. The pulp form of thepoly-p-phenylene terephthalamide fibers is available as a wet pulp or adry pulp and at various fiber lengths and various degrees offibrillation. The TWARON® 1099 para-aramid is formed from a TWARON®filament yarn having a diameter of about 12 μm and having less thanabout 1% of a surface finish. These yarns are then heavily fibrillatedto form the TWARON® 1099 para-aramid in the pulp form. The pulp form ofthe poly-p-phenylene terephthalamide fibers is discontinuous and doesnot exhibit a specific length. When processed, the pulp form breaks downinto fibers of different lengths. The aramid functions as a low densityfiller and improves mechanical properties of the insulation formed fromthe precursor composition.

While the examples described below include TWARON® type aramid pulp1099, other fibers may be used, such as glass, boron, boron nitride,silicon carbide, graphite, polyimide, polybenzimidazole,polybenzothiazole, polybenzamide, polybenzoxazole, polyethylene,cellulose, sisal, nylon, mineral wool, polyester, or combinationsthereof.

The carbon material of the precursor composition of the insulation maybe a conductive carbon material, depending on the desired properties ofthe uncured precursor composition or of the insulation, such as thedesired electrostatic discharge (ESD) properties. The carbon materialmay include carbon nanotubes, graphite, conductive carbon black, or acombination thereof. If insulative properties are desired, the carbonmaterial may not be present. If present, the carbon material may accountfor from about 5.0 parts to about 50.0 parts of the precursorcomposition of the insulation, such as from about 8.0 parts to about46.0 parts of the precursor composition of the insulation or from about20.0 parts to about 46.0 parts of the precursor composition of theinsulation.

The carbon material may include single-walled carbon nanotubes ormulti-walled carbon nanotubes, either in an undispersed form (e.g., araw material, such as a powder) or in a pre-dispersed form. Multi-walledcarbon nanotubes in the pre-dispersed form may include, but are notlimited to, those commercially available from Arkema Inc. (Exton, Pa.)under the GRAPHISTRENGTH® tradename, such as GRAPHISTRENGTH® EPDM 20,which contains the multi-walled carbon nanotubes pre-dispersed in EPDMat a concentration of about 17 wt % (about 20 parts). The multi-walledcarbon nanotubes may be present in the precursor composition of theinsulation at from about 3.0 parts to about 45.0 parts, such as fromabout 3.0 parts to about 10.0 parts, from about 15.0 parts to about 30.0parts, or from about 35.0 parts to about 45.0 parts. In someembodiments, the multi-walled carbon nanotubes are present in theprecursor composition at about 4.0 parts, about 23.5 parts, or about41.2 parts.

Other forms of carbon may be used in the precursor composition of theinsulation, such as graphite, expanded graphite, or expandable graphite.In some embodiments, the carbon material is expandable graphite. Theexpandable graphite may exhibit an expansion ratio of from about 30(ml/g) min to about 250 (ml/g) min and a carbon content of from about80% to about 99%, such as about 80%, about 85%, about 90%, about 95%, orabout 99%. The expandable graphite has an intercalant compound, such assulfuric acid, nitric acid, or acetic acid, between graphene layers ofthe expandable graphite. When the expandable graphite is exposed toheat, the intercalant compound is volatilized, which separates thegraphene layers and increases the volume of the graphene layers. Theexpandable graphite may have an average particle size of less than about75 μm, greater than about 75 μm, less than about 180 μm, greater thanabout 180 μm, less than about 250 μm, or greater than about 300 μm. Insome embodiments, the expandable graphite is expandable graphite 1722HTfrom Asbury Carbons Inc. (Asbury, N.J.). The expandable graphite may bepresent in the precursor composition of the insulation at from about 1.0part to about 15.0 parts, such as from about 2.0 parts to about 10.0parts, from about 3.0 parts to about 8.0 parts or from about 3.0 partsto about 5.0 parts. In some embodiments, the expandable graphite ispresent in the precursor composition at about 4.0 parts.

In some embodiments, the precursor composition may include carbonnanotubes and graphite. The carbon nanotubes may be multi-walled carbonnanotubes in the pre-dispersed form, such as GRAPHISTRENGTH® EPDM 20,and the graphite may be expandable graphite, such as expandable graphite1722HT from Asbury Carbons Inc. (Asbury, N.J.).

Without being bound by any theory, it is believed that the carbonmaterial provides ablative properties to the precursor composition ofthe insulation in addition to the ESD properties. It was unexpected thatthe carbon material would improve the ablative properties of theinsulation since carbon materials are known in the art to be difficultto disperse and ablative properties are usually improved for homogeneouscompositions. It is known in the art that carbon nanotubes agglomerateand are difficult to disperse in EPDM-based compositions. However, itwas unexpectedly found that the precursor compositions including themulti-walled carbon nanotubes and the expandable graphite exhibitedimproved ablative properties.

The antioxidant may be a hydroquinoline compound, such as a polymerized1,2-dihydro-2,2,4-trimethylquinoline, which is commercially availablefrom Vanderbilt Chemicals, LLC (Norwalk, Conn.) under the AGERITE®tradename. By way of example only, the antioxidant may be AGERITE® ResinD. The antioxidant may also be an amine compound, a phenol compound,another antioxidant, or combinations thereof, including combinationswith the polymerized 1,2-dihydro-2,2,4-trimethylquinoline. Theantioxidant may be present in the precursor composition of theinsulation at from about 0.35 part to about 0.75 part. In someembodiments, the antioxidant is AGERITE® Resin D, a polymerized1,2-dihydro-2,2,4-trimethylquinoline, and is present in the precursorcomposition of the insulation at about 0.5 part.

The filler may be zinc oxide, silica (silicon dioxide), magnesiumhydroxide, or a combination thereof. The zinc oxide may include, but isnot limited to, a propionic acid coated zinc oxide having a surface areaof from about 4.0 m²/g to about 6.0 m²/g and a particle size of fromabout 0.18 μm to about 0.27 μm, such as Zoco 672, which is commerciallyavailable from Zochem Inc. (Brampton, Canada). In addition to the powderform, zinc oxide in a pellet form may be used, such as Zoco 627. Thesilica may be an amorphous, precipitated silica, such as thatcommercially available from PPG Industries, Inc. (Pittsburgh, Pa.) underthe HI-SIL® tradename. By way of example only, HI-SIL® 233 silica havinga surface area (BET) of 135 m²/g may be used as the filler. Themagnesium hydroxide may be a non-halogenated, high purity powder, suchas that commercially available from Martin Marietta MagnesiaSpecialties, LLC (Baltimore, Md.) under the MAGSHIELD® tradename. By wayof example only, the magnesium hydroxide may be MAGSHIELD® S. The purityof the magnesium hydroxide may be greater than about 95%, such asgreater than about 97% or greater than about 98%. The magnesiumhydroxide may also provide flame retardance to the precursor compositionof the insulation. In some embodiments, the precursor compositionincludes zinc oxide and silica. In other embodiments, the precursorcomposition includes magnesium hydroxide.

The filler may be present in the precursor composition of the insulationat from about 0.5 part to about 10.0 parts, such as from about 1.0 partto about 10.0 parts, from about 0.5 part to about 5.0 parts, from about0.5 part to about 9.0 parts, or from about 1.0 part to about 5.0 parts.Zinc oxide may be present in the precursor composition of the insulationat from about 2.1 parts to about 4.5 parts, the amorphous, precipitatedsilica may be present in the precursor composition of the insulation atfrom about 3 parts to about 8 parts, and the magnesium hydroxide may bepresent in the precursor composition of the insulation at from about 0.5part to about 8 parts. In some embodiments, the filler includes Zoco672, the zinc oxide, and HI-SIL® 233, the amorphous, precipitatedsilica. The zinc oxide is present in the precursor composition of theinsulation at about 3.0 parts and the amorphous, precipitated silica ispresent in the precursor composition of the insulation at about 6.0parts. In other embodiments, the filler includes MAGSHIELD® S, themagnesium hydroxide, which is present in the precursor composition ofthe insulation at about 1.0 part or about 4.0 parts.

The flame retardant may be a chlorinated organic compound, such as asolid chlorinated paraffin, a polychlorinated polycyclic compound, achloroprene, or combinations thereof. The flame retardant may be presentin the precursor composition of the insulation at from about 5.0 partsto about 30.0 parts, such as from about 5.0 parts to about 10.0 parts,from about 10.0 parts to about 25.0 parts, or from about from about 15.0parts to about 30.0 parts. The solid chlorinated paraffin may include,but is not limited to, that commercially available from Dover ChemicalCorporation (Dover, Ohio) under the CHLOREZ® tradename. The solidchlorinated paraffin may be a 70% chlorinated paraffin, such as CHLOREZ®700. In some embodiments, the solid chlorinated paraffin is present inthe precursor composition of the insulation at about 20 parts. In otherembodiments, the solid chlorinated paraffin is present in the precursorcomposition of the insulation at about 8 parts. The flame retardant mayalso be a polychlorinated polycyclic compound, such as DECHLORANE PLUS®25, which is commercially available from Occidental Chemical Corp.(Dallas, Tex.). The chloroprene may be Neoprene GRT, which is asulfur-modified polychloroprene and is commercially available from DenkaPerformance Elastomer, LLC. (New Castle, Del.). Combinations of theflame retardants may also be used. In some embodiments, the flameretardant includes the solid chlorinated paraffin at about 20 parts. Inother embodiments, the flame retardant includes the solid chlorinatedparaffin at about 8 parts, the polychlorinated polycyclic compound atabout 8 parts, and the chloroprene at about 10 parts.

The processing aid may be a fatty acid or fatty acid derivative, such asthat commercially available from PMC Biogenix, Inc. (Memphis, Tenn.)under the INDUSTRENE® tradename. The fatty acid may be a stearic acid(C₁₇H₃₅CO₂H), such as INDUSTRENE® B. The stearic acid may be present inthe precursor composition of the insulation at from about 0.35 part toabout 0.75 part. In some embodiments, the stearic acid is present in theprecursor composition of the insulation at about 0.5 part.

The plasticizer may be an aliphatic resin, such as that commerciallyavailable from TOTAL Cray Valley (Exton, Pa.) under the WINGTACK®tradename. The aliphatic resin may be a five carbon (C5) petroleumhydrocarbon, such as WINGTACK® 95. The aliphatic resin may be present inthe precursor composition of the insulation at from about 4.0 parts toabout 15.0 parts, such as from about 8.0 parts to about 12.0 parts orfrom about 10.0 parts to about 11.0 parts. In some embodiments, thealiphatic resin is present in the precursor composition of theinsulation at about 10 parts. In other embodiments, the aliphatic resinis present in the precursor composition of the insulation at about 11parts.

The co-agent may be a low volatility trifunctional monomer, such astrimethylolpropane trimethacrylate, which is commercially available fromSartomer Americas (Exton, Pa.) as SR350. Alternatively, the co-agent maybe a poly(butadiene) resin, such as a high vinyl poly(butadiene), whichis commercially available from Cray Valley USA, LLC (Exton, Pa.) underthe RICON® tradename. One or more co-agents may be used. The co-agentmay be present in the precursor composition of the insulation at fromabout 1.0 part to about 12.0 parts, such as from about 2.0 parts toabout 10.0 parts or from about 2.0 parts to about 8 parts. In someembodiments, the trimethylolpropane trimethacrylate is present in theprecursor composition of the insulation at about 5 parts. In otherembodiments, the trimethylolpropane trimethacrylate is present in theprecursor composition of the insulation at about 3.6 parts.

The curative may be a crosslinking peroxide, such as that commerciallyavailable from Arkema Inc. (Exton, Pa.) under the LUPEROX® tradename.One or more curatives may be used. By way of example only, the curativemay be LUPEROX® 231 XL40, which is a 40% active dispersion of LUPEROX®231 (1,1-di-(t-butylperoxy)-3,3,5-trimethylcyclohexane) polymerinitiator on calcium carbonate. The1,1-di-(t-butylperoxy)-3,3,5-trimethylcyclohexane) polymer initiator mayalso be used in pure form, such as without the inert support.Alternatively, the curative may be dicumyl peroxide (DCP), which may beused in pure form or with an inert support. The curative may be presentin the precursor composition of the insulation at from about 1.0 part toabout 12.0 parts, such as from about 1.0 part to about 6.0 parts or fromabout 5.0 parts to about 12 parts. In some embodiments, the curative ispresent in the precursor composition of the insulation at about 8.0parts. In other embodiments, the curative is present in the precursorcomposition of the insulation at about 7.0 parts. In yet otherembodiments, the curative is present in the precursor composition of theinsulation at about 5.7 parts.

While specific examples of the antioxidant, co-agent, and curative areprovided above, other antioxidants, co-agents, and/or curatives may beused depending on the desired shelf life of the uncured precursorcomposition or of the insulation, or on the desired mechanicalproperties of the insulation. The antioxidant may be selected dependingon whether the precursor composition is to have an increased ordecreased shelf life. Other co-agents and curatives may be selecteddepending on the desired mechanical properties or cure temperaturerequirements of the insulation.

The precursor compositions of the insulation may include feweringredients than the conventional aramid-filled EPDM insulations,reducing the cost and complexity of manufacturing an article includingthe insulation. In some embodiments, the precursor composition of theinsulation has 12 or 13 ingredients, compared to at least 16 ingredientsin the conventional aramid-filled EPDM insulations. By including feweringredients, obsolescence issues with the ingredients may be reduced,such as qualification costs for future materials. The ingredients mayalso be commercially available, which further reduces obsolescenceissues. The precursor compositions according to embodiments of thedisclosure may also have a longer shelf life at room temperature (fromabout 20° C. to about 25° C.) compared to the conventional aramid-filledEPDM insulations, which have a shelf life at about 0° C. for up to oneyear.

The precursor composition may be prepared by combining (e.g., mixing)the EPDM, aramid, carbon material, antioxidant, filler, flame retardant,processing aid, plasticizer, co-agent, and curative in a mixer, such asan internal mixer. All of the ingredients are solid at room temperatureand are combined in the mixer to form a homogeneous precursorcomposition. The ingredients, including the aramid, are homogeneouslydispersed in the precursor composition. The pulp form of the aramid usedin the precursor composition does not have a specified length and breaksdown into shorter length fibers during processing of the precursorcomposition. Shear in the mixer generates a sufficient amount of heat tosoften the EPDM, enabling the homogeneous precursor composition to beformed without adding a solvent. Thus, the precursor composition may beprepared by a solvent-less process. Since no solvents are used, asolvent removal process, such as drying or solvent evaporation, is notneeded before curing the precursor composition to form the insulation.

The precursor composition may be shaped into its desired form, such asby extruding, calendaring, or compression molding. In some embodiments,the precursor composition is extrudable. The extrudability of theprecursor composition is comparable to that of the conventionalaramid-filled EPDM insulations. The precursor composition may exhibit asufficiently low viscosity such that the precursor composition has aflowable consistency before curing. As used herein, the term “flowable”means and includes a sufficiently low viscosity that enables theprecursor composition to change shape or direction substantiallyuniformly in response to heat and/or shear, such that the precursorcomposition readily flows out of a container at room temperature. Theflow behavior and extrudability of the precursor composition reduces thecost of manufacturing the rocket motor because the precursor compositionor resulting insulation may be applied to the rocket motor by automatedlayup processes. By reducing or eliminating manual layup processes, thecost of manufacturing the rocket motor may be reduced. By way of exampleonly, the precursor composition may be calendared to a desiredthickness, such as a thickness of about 0.1 inch (about 0.254 cm). Onceprepared, the precursor composition may be applied to the rocket motoror other article and cured. Alternatively, the precursor composition maybe stored until use. The precursor composition may be used as internalinsulation or external insulation of a rocket motor, or as a shear plydepending on the configuration of the rocket motor. The precursorcomposition may be used as a shear ply to couple a case of the rocketmotor to a rocket skirt. The precursor composition may be applied to therocket motor by hand layup or by automated layup processes.

In addition to being used as insulation in rocket motors, the insulationmay be used in other articles where protection from heat and gases isdesired. For example, the insulation may be used for heat and gasprotection in under-the-hood applications in automobiles. The insulationmay also be used in conveyor belts and in noise-damping applications inautomobile and other fields. In addition, since the insulation may beextruded, compression molded, or calendared, the insulation may be usedin routine rubber applications including, but not limited to, suchapplications as hoses, gaskets, seals, isolators and mounts, cushions,air emission hoses, and dock fenders.

Methods of applying the precursor composition to the rocket motor andcuring the precursor composition are known in the art and, therefore,are not described in detail herein. The precursor composition may beapplied to a case of the rocket motor and cured, forming the insulationon an inner surface of the case. While the curing may occur at roomtemperature (about 20° C.-25° C.), the curing may be accelerated byapplying at least one of heat and pressure as known in the art.Alternatively, the precursor composition may be applied to a mandrel,cured to form the insulation, and subsequent layers of the rocket motorformed over the insulation. Alternatively, the precursor composition maybe applied to the mandrel, subsequent layers of the rocket motor formedover the precursor composition, and the entire assembly curedsubstantially simultaneously.

As shown in FIGS. 1 and 2, insulation 8 may be used in a rocket motor 2.The rocket motor 2 includes a case 4 produced from a rigid, durablematerial, such as a metal or composite. The case 4 houses a solidpropellant 6 that combusts to provide the thrust necessary to propel therocket motor 2. The insulation 8 is applied to an inner surface of thecase 4, and is present between the case 4 of the rocket motor 2 and thepropellant 6. An optional liner 10 may be present between the insulation8 and the propellant 6. Methods for loading the case 4 with theinsulation 8, optional liner 10, and propellant 6 are known in the artand, therefore, are not described in detail herein. Nozzle 12 isoperatively associated with the case 4 to receive combustion productsgenerated by combustion of the propellant 6 and to expel the combustionproducts, generating thrust to propel the rocket motor 2. During use andoperation of the rocket motor 2, the insulation 8 protects the case 4from heat and particle streams that are generated by combustion of thepropellant 6.

While the insulation 8 is shown as being applied to the inner surface ofthe case 4, the insulation 8 may be used on other regions of the rocketmotor 2, either internally, externally, or both. For example, theinsulation 8 may provide ablative protection to an external bulk of thecase 4 and nozzle 12. Additionally, while the insulation 8 may be usedfor insulating a solid rocket motor and other large-scale motors, theinsulation may also be used with other motors, such as biliquid, hybridand reverse hybrid motors, or with rocket motor-propelled missiles. Asingle formulation of the insulation 8 may be used in multiple locationsin the rocket motor 2. Alternatively, different formulations of theinsulation 8 may also be used in the rocket motor 2, with precursorcompositions of the insulation 8 differing in that some include thearamid as described herein and others are fiber-free as described inU.S. patent application Ser. No. 15/726,731, filed Oct. 6, 2017, andSer. No. 15/461,339, filed on Mar. 16, 2017, the disclosure of each ofwhich is incorporated by reference herein in its entirety. The differentformulations of the insulation 8 may include substantially the same oridentical ingredients, with relative amounts of the ingredients beingdifferent.

A method of insulating the rocket motor 2 is also described. The methodcomprises producing the precursor composition that includes theingredients described above. The precursor composition is deposited on,or applied to, the inner surface of the case 4 of the rocket motor 2.The precursor composition is subsequently cured to form the insulation8. The rocket motor 2 may also include multiple precursor compositionsof the insulation 8 having similar or identical ingredients. Since theseprecursor compositions of the insulation 8 include similar or identicalingredients, the precursor compositions may be cured substantiallysimultaneously in the rocket motor 2, reducing fabrication costs andtime.

The insulation 8 formed from precursor compositions according toembodiments of the disclosure may exhibit comparable or improvedmechanical and ablative properties and comparable or improved processingcharacteristics compared to the conventional aramid-filled EPDM-basedinsulations. By way of example only, the insulation 8 formed from theprecursor compositions may exhibit comparable or improved modulus,stress capability, and strain capability compared to the conventionalaramid-filled EPDM-based insulations. The insulation 8 may also havebetter tack and ESD properties compared to the conventionalaramid-filled EPDM insulations. The insulation 8 may also be compatiblewith the solid propellant 6 used in the rocket motor 2 and non-permeableto gases produced as volatile, combustion products during use of theinsulation. The insulation 8 formed from the precursor compositionsaccording to embodiments of the disclosure may also have a longer shelflife at room temperature (from about 20° C. to about 25° C.) compared tothe conventional aramid-filled EPDM-based insulations, which have ashelf life at about 0° C. for up to one year.

The following examples serve to explain embodiments of the disclosure inmore detail. These examples are not to be construed as being exhaustiveor exclusive as to the scope of this disclosure.

EXAMPLES Example 1 Precursor Composition Formulations

Precursor compositions including the ingredients shown in Table 1 wereproduced. Initial formulations including the ingredients shown in Table1 were prepared.

TABLE 1 Formulations of Precursor Compositions EPDM Composition EPDM BEPDM Composition A Amount Composition C Ingredient Amount (parts)(parts) Amount (parts) NORDEL ® IP 4520 65.8 0 0 EPDM KELTAN ® 2650 080.5 100 EPDM AGERITE ® Resin D 0.5 0.5 0.5 Zoco 672 3.0 0 0 HI-SIL ®233 6.0 0 0 MAGSHIELD ® S 0 4.0 1.0 CHLOREZ ® 700 20.0 20.0 8.0DECHLORANE 0 0 8.0 PLUS ® Expandable Graphite 4.0 4.0 4.0 1722HTGRAPHISTRENGTH ® 41.2 23.5 0 EPDM 20^(a) Multi-walled Carbon 0 0 4.0Nanotubes^(b) INDUSTRENE ® B 0.5 0.5 0.5 WINGTACK ® 95 10.0 11.0 10.0SR350 3.6 5.0 5.0 TWARON ® pulp type 21.0 20.0 20.0 1099 Neoprene GRT 00 10.0 LUPEROX ® 231 XL40 7.0 8.0 5.72 ^(a)A dispersion of multi-walledcarbon nanotubes in 20% EPDM ^(b)An undispersed form of multi-walledcarbon nanotubes

Each of the ingredients was commercially available and was used asreceived. The ingredients in Table 1 were added to an internal mixer andcombined to produce the precursor compositions.

Based on the mechanical, physical, and thermal properties of theformulations in Table 1, additional formulations were prepared and areshown in Tables 2-7. Each of the ingredients was commercially availableand was used as received. The ingredients of the respective formulationsF-P were added to an internal mixer and combined to produce therespective precursor compositions. The formulations F-P were mixed at a300 g scale or 5 pound scale.

To determine the effect of aramid loading and a DCP-based cure system,formulations including various amounts of the aramid fibers and DCP wereprepared and are shown in Table 2.

TABLE 2 Formulations of Precursor Compositions EPDM EPDM EPDM EPDM EPDMEPDM Comp. F Comp. G Comp. H Comp. I Comp. J Comp. K Amount AmountAmount Amount Amount Amount Ingredient (parts) (parts) (parts) (parts)(parts) (parts) KELTAN ® 2650 EPDM 65.8 65.8 65.8 65.8 65.8 65.8CHLOREZ ® 700 18.0 18.0 18.0 18.0 18.0 18.0 AGERITE ® Resin D 0.5 0.50.5 0.5 0.5 0.5 INDUSTRENE ® B 0.5 0.5 0.5 0.5 0.5 0.5 ExpandableGraphite 1722HT 3.0 3.0 3.0 3.0 3.0 3.0 GRAPHISTRENGTH ® EPDM 20^(a)41.2 41.2 41.2 41.2 41.2 41.2 TWARON ® pulp type 1099 17.0 15.0 13.017.0 15.0 13.0 MAGSHIELD ® S 3.0 3.0 3.0 3.0 3.0 3.0 RICON ® 150 2.0 2.02.0 2.0 2.0 2.0 Dicumyl peroxide 1.75 1.75 1.75 2.0 2.0 2.0 ^(a)Adispersion of multi-walled carbon nanotubes in 20% EPDM

To determine the effect of the flame retardant, formulations includingvarious amounts of the solid chlorinated paraffin were prepared and areshown in Table 3.

TABLE 3 Formulations of Precursor Compositions EPDM Composition EPDM HEPDM Composition G Amount Composition I Ingredient Amount (parts)(parts) Amount (parts) KELTAN ® 2650 65.8 65.8 65.8 EPDM CHLOREZ ® 70018.0 19.0 21.0 AGERITE ® Resin D 0.5 0.5 0.5 INDUSTRENE ® B 0.5 0.5 0.5Expandable Graphite 3.0 3.0 3.0 1722HT GRAPHISTRENGTH ® 41.2 41.2 41.2EPDM 20^(a) TWARON ® pulp type 15.0 15.0 15.0 1099 MAGSHIELD ® S 3.0 3.03.0 RICON ® 150 2.0 2.0 2.0 Dicumyl peroxide 1.75 1.75 1.75 ^(a)Adispersion of multi-walled carbon nanotubes in 20% EPDM

To determine the effect of the plasticizer, formulations includingvarious amounts of the C5 petroleum hydrocarbon were prepared and areshown in Table 4.

TABLE 4 Formulations of Precursor Compositions EPDM Composition EPDM JEPDM Composition H Amount Composition K Ingredient Amount (parts)(parts) Amount (parts) KELTAN ® 2650 65.8 65.8 65.8 EPDM CHLOREZ ® 70019.0 19.0 21.0 AGERITE ® Resin D 0.5 0.5 0.5 INDUSTRENE ® B 0.5 0.5 0.5WINGTACK ® 95 0 2.0 4.0 Expandable Graphite 3.0 3.0 3.0 1722HTGRAPHISTRENGTH ® 41.2 41.2 41.2 EPDM 20^(a) TWARON ® pulp type 15.0 15.015.0 1099 MAGSHIELD ® S 3.0 3.0 3.0 RICON ® 150 2.0 2.0 2.0 Dicumylperoxide 1.75 1.75 1.75 ^(a)A dispersion of multi-walled carbonnanotubes in 20% EPDM

To determine the effect of the co-agent, formulations including variousamounts of the poly(butadiene) resin were prepared and are shown inTable 5.

TABLE 5 Formulations of Precursor Compositions EPDM EPDM Composition LComposition M Ingredient Amount (parts) Amount (parts) KELTAN ® 265065.8 65.8 EPDM CHLOREZ ® 700 15.0 15.0 AGERITE ® Resin D 0.5 0.5INDUSTRENE ® B 0.5 0.5 WINGTACK ® 95 4.0 4.0 Expandable Graphite 3.0 3.01722HT GRAPHISTRENGTH ® 41.2 41.2 EPDM 20^(a) TWARON ® pulp type 11.011.0 1099 MAGSHIELD ® S 3.0 3.0 RICON ® 150 2.0 5.0 Dicumyl peroxide1.75 1.75 ^(a)A dispersion of multi-walled carbon nanotubes in 20% EPDM

To determine the effect of the curative, formulations including variousamounts of the DCP were prepared and are shown in Table 6.

TABLE 6 Formulations of Precursor Compositions EPDM Composition EPDM LEPDM Composition N Amount Composition O Ingredient Amount (parts)(parts) Amount (parts) KELTAN ® 2650 65.8 65.8 65.8 EPDM CHLOREZ ® 70015.0 15.0 15.0 AGERITE ® Resin D 0.5 0.5 0.5 INDUSTRENE ® B 0.5 0.5 0.5WINGTACK ® 95 4.0 4.0 4.0 Expandable Graphite 3.0 3.0 3.0 1722HTGRAPHISTRENGTH ® 41.2 41.2 41.2 EPDM 20^(a) TWARON ® pulp type 11.0 11.011.0 1099 MAGSHIELD ® S 3.0 3.0 3.0 RICON ® 150 2.0 2.0 2.0 Dicumylperoxide 1.5 1.75 2.0 ^(a)A dispersion of multi-walled carbon nanotubesin 20% EPDM

To determine the effect of the EPDM, formulations including varioustypes of EPDM were prepared and are shown in Table 7.

TABLE 7 Formulations of Precursor Compositions EPDM EPDM Composition LComposition P Ingredient Amount (parts) Amount (parts) KELTAN ® 265065.8 0.0 EPDM NORDEL ® IP 4520 0.0 65.8 EPDM CHLOREZ ® 700 15.0 15.0AGERITE ® Resin D 0.5 0.5 INDUSTRENE ® B 0.5 0.5 WINGTACK ® 95 4.0 4.0Expandable Graphite 3.0 3.0 1722HT GRAPHISTRENGTH ® 41.2 41.2 EPDM20^(a) TWARON ® pulp type 11.0 11.0 1099 MAGSHIELD ® S 3.0 3.0 RICON ®150 2.0 5.0 Dicumyl peroxide 1.75 1.75 ^(a)A dispersion of multi-walledcarbon nanotubes in 20% EPDM

Example 2 Mechanical, Physical, and Thermal Properties

The mechanical, physical, and thermal properties of the precursorcompositions described in Table 1 were determined and are shown in Table8. The mechanical, physical, and thermal properties were determined byconventional techniques. The properties of EPDM Compositions A-C werecompared to two conventional, aramid-filled EPDM compositions, which areindicated in Table 8 as “EPDM Comparative Composition D” and “EPDMComparative Composition E.” The EPDM Comparative Compositions D and Eincluded a larger number of ingredients than the EPDM Compositions A-C.

TABLE 8 Mechanical, Physical, and Thermal Properties of PrecursorCompositions of Table 1 EPDM EPDM EPDM EPDM EPDM Comparative ComparativeProperty Composition A Composition B Composition C Composition DComposition E Number of 12 11 13 16 18 Ingredients Specific 1.07 1.051.04   1-1.04 1.18-1.22 Gravity (g/ml) Mooney 52.3 39 50 20-50 60-90Viscosity at 212° F. Tack Time 0 0 11 0 0 (sec) ESD Surface 2.17 × 10⁶Insulator  3.0 × 10⁷ Insulator Insulator Resistivity (ohms/sq) ESDVolume 3.92 × 10⁷ Insulator 4.05 × 10⁶ Insulator Insulator Resistivity(ohms.cm) Modulus (psi) 24300 13800 10877 4190 8460 Stress 986 1200 16601440 2240 Capability (psi) Strain (%) 32 34 29.4 36.3 29.1 PropellantCompatible Compatible Compatible Compatible Compatible CompatibilityPermeability Non- Non- Non- Non- Non- at 20% Strain permeable permeablepermeable permeable permeable Coefficient of 0 to 489 −9 to +530 +20 to+375 −0.25 to +405 +15 to +420 Thermal Expansion (in/in ° F. × 10⁻⁶)Thermal 0.00025 0.00021 0.00021 0.00014 0.00018 Diffusivity (in²/sec)Specific Heat 1.840 1.971 1.957 1.830 1.446 ESD ESD Insulating ESDInsulating Insulating

EPDM Compositions A-C exhibited comparable or improved modulus, stresscapability, and strain capability compared to the EPDM ComparativeCompositions D and E. Each of the EPDM Compositions A-C was alsocompatible with conventional propellants including, but not limited to,NEPE, PBAN, and HTPB. The EPDM Compositions A-C were also determined tobe non-permeable to gases produced as volatile, combustion productsduring use of the precursor composition as insulation. EPDM CompositionsA and C also exhibited comparable or improved ESD properties compared toEPDM Comparative Compositions D and E.

The mechanical, physical, and thermal properties of the precursorcompositions described in Table 2 were determined and are shown in Table9. The mechanical, physical, and thermal properties were determined byconventional techniques.

TABLE 9 Mechanical, Physical, and Thermal Properties of PrecursorCompositions of Table 2 EPDM EPDM EPDM EPDM EPDM EPDM Property Comp. FComp. G Comp. H Comp. I Comp. J Comp. K Specific Gravity (g/ml) 1.0331.029 1.025 1.033 1.029 1.025 Tack Time (sec) 16 25 31 29 32 29 Strainat Max Stress (%) 29.7 40.6 44.9 30.5 35.8 38.8 Tensil Strength (psi)1080 802 741 975 786 798 Torch data 0.98 0.98 1.03 0.99 1.06 1.01

Each of EPDM Compositions F-K exhibited desirable properties.

The mechanical, physical, and thermal properties of the precursorcompositions described in Table 3 were determined and are shown in Table10. The mechanical, physical, and thermal properties were determined byconventional techniques.

TABLE 10 Mechanical, Physical, and Thermal Properties of PrecursorCompositions of Table 3 EPDM EPDM EPDM Property Composition GComposition H Composition I Specific 1.029 1.031 1.036 Gravity (g/cc)Tack Time 25 34 32 (sec) Strain at 40.6 32.5 40.2 Max Stress (%) Tensile802 970 865 Strength (psi) Torch data 0.98 1.07 1.06

Each of EPDM Compositions G-I exhibited desirable properties.

The mechanical, physical, and thermal properties of the precursorcompositions described in Table 4 were determined and are shown in Table11. The mechanical, physical, and thermal properties were determined byconventional techniques.

TABLE 11 Mechanical, Physical, and Thermal Properties of PrecursorCompositions of Table 4 EPDM EPDM EPDM Property Composition HComposition J Composition K Specific 1.031 1.032 1.032 Gravity (g/cc)Tack Time 34 31 33 (sec) Strain at 32.5 36.1 37.3 Max Stress (%) Tensile970 892 861 Strength (psi) Torch data 1.07 1.06 1.06

Each of EPDM Compositions H, J, and K exhibited desirable properties.

The mechanical, physical, and thermal properties of the precursorcompositions described in Table 5 were determined and are shown in Table12. The mechanical, physical, and thermal properties were determined byconventional techniques.

TABLE 12 Mechanical, Physical, and Thermal Properties of PrecursorCompositions of Table 5 EPDM EPDM Property Composition L Composition MSpecific 1.014 1.007 Gravity (g/cc) Tack Time 44 37 (sec) Strain at 43.242.8 Max Stress (%) Tensile 865 902 Strength (psi) Torch data 0.9951.034

Each of EPDM Compositions L and M exhibited desirable properties.

The mechanical, physical, and thermal properties of the precursorcompositions described in Table 6 were determined and are shown in Table13. The mechanical, physical, and thermal properties were determined byconventional techniques.

TABLE 13 Mechanical, Physical, and Thermal Properties of PrecursorCompositions of Table 6 EPDM EPDM EPDM Property Composition NComposition L Composition O Specific 1.016 1.014 1.009 Gravity (g/cc)Tack Time 37 44 29 (sec) Strain at 52.5 43.2 37.2 Max Stress (%) Tensile818 865 883 Strength (psi) Torch data 1.064 0.995 1.010

Each of EPDM Compositions N, L, and O exhibited desirable properties.

The mechanical, physical, and thermal properties of the precursorcompositions described in Table 7 were determined and are shown in Table14. The mechanical, physical, and thermal properties were determined byconventional techniques.

TABLE 14 Mechanical, Physical, and Thermal Properties of PrecursorCompositions of Table 7 EPDM EPDM Property Composition L Composition PSpecific 1.014 1.015 Gravity (g/cc) Tack Time 44 48.3 (sec) Strain at43.2 30.9 Max Stress (%) Tensile 865 800 Strength (psi) Torch data 0.9951.123

Each of EPDM Compositions L and P exhibited desirable properties.

Example 3 Flow and Extrudability Properties

The rubber flow behavior of EPDM Compositions A-C described in Table 1was determined by conventional techniques. The precursor compositionswere placed in a spider mold and cured. Each of EPDM Compositions A-C,respectively, exhibited good rubber flow characteristics in the spidermold, as shown in FIGS. 3-5.

The extrusion ability of EPDM Compositions A-C described in Table 1 wasdetermined by conventional techniques. As shown in FIGS. 6-8, each ofEPDM Compositions A-C, respectively, exhibited good extrudability.

Example 4 Ablative Properties

The ablative properties of EPDM Compositions A-C described in Table 1were determined in a low Mach seventy pound char (SPC) motor test. TheSPC motor test simulated conventional temperature and pressureconditions in low velocity, mid velocity, and high velocity sections ofthe char motor. The diameter of the char motor varies in these threesections, with the char motor having a relatively large diameter in thelow velocity section while in the high velocity section, the char motorhas a relatively small diameter. The diameter of the char motor at agiven location determines the amount of exposure that the insulationreceives. If the diameter is small, that section of the char motor willbe exposed to more gases and will be more prone to erosion than if thediameter is large. Therefore, a particular portion of the char motor inthe low velocity section is exposed to a reduced amount of gases incomparison to a particular portion of the char motor in the highvelocity section.

Each of EPDM Compositions A-C was formed into a thin sheet, cured, andassembled into the char motor by conventional techniques. The thicknessof the insulation was measured at selected intervals, nominally one inchapart, before firing the char motor. The weight of the part was alsorecorded before firing the char motor. After firing, the char motor wasdisassembled, and the thickness and weight of the insulation weremeasured again. The rate at which each of the insulations is reduced oreroded is expressed in terms of the reduction of the thickness of theinsulation per second, and is referred to as the material affected rateor material ablation rate (“MAR”). The MAR of the insulations wasdetermined by subtracting the post-fired thickness of virgin insulation(i.e., after the char had been removed) at a given point from thepre-fired thickness at the same point and dividing the result by theburn time of the char motor. The MAR and percent weight loss areindicators of damage (e.g., ablation) to the insulation, where lowernumbers indicate better insulative and ablative performance.

The MAR was measured for the low velocity, mid velocity, and highvelocity sections of the char motor and is shown in FIGS. 9-11 for EPDMCompositions A-C, respectively, along with the MAR for EPDM ComparativeCompositions D and E.

The percent weight loss of the insulations was determined as a functionof the pre-fired weight for the low velocity, mid velocity, and highvelocity sections of the char motor and is shown in FIGS. 12-14 for EPDMCompositions A-C, respectively, along with the percent weight loss forEPDM Comparative Compositions D and E.

The average MAR for the insulations formed from the precursorcompositions described in Example 1 was measured for the low velocity,mid velocity, and high velocity sections of the char motor and is shownin FIGS. 15-17 for EPDM Compositions A-C, respectively, along with theMAR for EPDM Comparative Compositions D and E.

Each of EPDM Compositions A-C exhibited comparable or improved ablativeperformance compared to the conventional, aramid-filled EPDMcompositions (EPDM Comparative Compositions D and E).

While the disclosure may be susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, it should be understood that the invention is not intended tobe limited to the particular forms disclosed. Rather, the invention isto cover all modifications, equivalents, and alternatives falling withinthe scope of the following appended claims and their legal equivalents.

What is claimed is:
 1. A precursor composition, comprising, beforecuring: ethylene propylene diene monomer (EPDM), an aramid, and a carbonmaterial comprising carbon nanotubes, graphite, or a combinationthereof.
 2. The precursor composition of claim 1, wherein the precursorcomposition comprises the carbon material at from about 5.0 parts toabout 50.0 parts.
 3. The precursor composition of claim 1, wherein theprecursor composition comprises the carbon material at from about 8.0parts to about 46.0 parts.
 4. The precursor composition of claim 1,wherein the precursor composition comprises the carbon material at fromabout 20.0 parts to about 46.0 parts.
 5. The precursor composition ofclaim 1, wherein the graphite comprises expandable graphite.
 6. Theprecursor composition of claim 5, wherein the precursor compositioncomprises the expandable graphite at from about 2.0 parts to about 10.0parts.
 7. The precursor composition of claim 1, wherein the carbonmaterial comprises carbon nanotubes and expandable graphite and thecarbon material comprises from about 8.0 parts to about 46.0 parts. 8.The precursor composition of claim 1, wherein the aramid comprisespoly-p-phenylene terephthalamide.
 9. The precursor composition of claim1, wherein the aramid comprises fibers of poly-p-phenyleneterephthalamide.
 10. The precursor composition of claim 1, wherein thearamid comprises from about 5.0 parts to about 25.0 parts of theprecursor composition.
 11. The precursor composition of claim 1, whereinthe aramid comprises poly-p-phenylene terephthalamide fibers in pulpform.
 12. The precursor composition of claim 11, wherein the precursorcomposition comprises the EPDM, the poly-p-phenylene terephthalamidefibers in pulp form, the carbon nanotubes and expandable graphite,magnesium hydroxide, a polymerized 1,2-dihydro-2,2,4-trimethylquinoline,a solid chlorinated paraffin, stearic acid, a five carbon petroleumhydrocarbon, trimethylolpropane trimethacrylate, and1,1-di-(t-butylperoxy)-3,3,5-trimethylcyclohexane) polymer.
 13. Theprecursor composition of claim 11, wherein the precursor compositioncomprises the EPDM, the poly-p-phenylene terephthalamide fibers in pulpform, the carbon nanotubes and expandable graphite, magnesium hydroxide,a polymerized 1,2-dihydro-2,2,4-trimethylquinoline, a solid chlorinatedparaffin, a polychlorinated polycyclic compound, a chloroprene, stearicacid, a five carbon petroleum hydrocarbon, trimethylolpropanetrimethacrylate, and 1,1-di-(t-butylperoxy)-3,3,5-trimethylcyclohexane)polymer.
 14. The precursor composition of claim 11, wherein theprecursor composition comprises the EPDM, the poly-p-phenyleneterephthalamide fibers in pulp form, the carbon nanotubes and expandablegraphite, zinc oxide, silica, a polymerized1,2-dihydro-2,2,4-trimethylquinoline, a solid chlorinated paraffin,stearic acid, a five carbon petroleum hydrocarbon, trimethylolpropanetrimethacrylate, and 1,1-di-(t-butylperoxy)-3,3,5-trimethylcyclohexane)polymer.
 15. A precursor composition, comprising, before curing:ethylene propylene diene monomer (EPDM); aramid fibers; a carbonmaterial; an antioxidant; a chlorinated organic compound; a fillerselected from the group consisting of zinc oxide, silica, magnesiumhydroxide, and combinations thereof; stearic acid; a five carbonpetroleum hydrocarbon; trimethylolpropane trimethacrylate or apoly(butadiene) resin; and1,1-di-(t-butylperoxy)-3,3,5-trimethylcyclohexane) polymer or dicumylperoxide.
 16. The precursor composition of claim 15, wherein theantioxidant comprises a hydroquinoline compound, an amine compound, aphenol compound, or combinations thereof.
 17. The precursor compositionof claim 15, wherein the chlorinated organic compound comprises a solidchlorinated paraffin, a polychlorinated polycyclic compound, achloroprene, or combinations thereof.
 18. The precursor composition ofclaim 15, wherein the EPDM comprises from about from about 60 parts toabout 110 parts of the precursor composition, the aramid fibers comprisefrom about 10.0 parts to about 25.0 parts of the precursor composition,and the carbon material comprises from about 8.0 parts to about 46.0parts of the precursor composition.
 19. A rocket motor, comprising: acase, an insulation on at least a portion of the case, and a propellantin the case, the insulation comprising: a reaction product of ethylenepropylene diene monomer (EPDM), an aramid, and a carbon materialcomprising carbon nanotubes, graphite, or a combination thereof.
 20. Therocket motor of claim 19, wherein the insulation on the case comprisesthe insulation on an inner surface of the case.
 21. The rocket motor ofclaim 19, wherein the insulation on the case comprises the insulation onan outer surface of the case.
 22. The rocket motor of claim 19, whereinthe insulation is present on multiple portions of the case.
 23. A methodof insulating a rocket motor, comprising: applying a precursorcomposition of an insulation to at least a portion of a rocket motor,the precursor composition comprising ethylene propylene diene monomer(EPDM), an aramid, and a carbon material comprising carbon nanotubes,graphite, or a combination thereof; and curing the precursor compositionto form the insulation.
 24. The method of claim 23, wherein applying aprecursor composition of an insulation to at least a portion of a rocketmotor comprises applying the precursor composition to multiple portionsof the rocket motor.
 25. The method of claim 24, wherein curing theprecursor composition to form the insulation comprises simultaneouslycuring the precursor composition on the multiple portions of the rocketmotor.
 26. The method of claim 23, further comprising applying anotherprecursor composition of an insulation to at least another portion ofthe rocket motor.
 27. The method of claim 26, wherein applying anotherprecursor composition of an insulation to at least another portion ofthe rocket motor comprises applying the another precursor compositioncomprising a fiber-free EPDM composition.
 28. The method of claim 26,wherein curing the precursor composition to form the insulationcomprises simultaneously curing the precursor composition and theanother precursor composition.